Study On Power System Of Highfrequency High-voltage And High-power X-ray Machine

X-ray machines are widely used in medical diagnosis,treatment and protection.Today,X-ray machines tend to be more digital,miniaturized,and intelligent.In recent years,foreign large-scale enterprises have always led the overall development level of X-ray machines.On the other hand,domestic companies are always catching up due to late start and slow technological upgrading.After nearly 20 years of research and learning,China has made remarkable progress in high-power X-ray machines and has independently developed a 50 kW X-ray machine high-voltage generator(DC high-voltage power supply),but its working performance and technological level comparing foreign advanced products The gap is obvious.The higher the operating frequency of the X-ray machine DC high-voltage power supply,the more conducive to reducing the size and weight of the X-ray machine;In addition,the more stable the system operation,the higher the precision,the actual imaging will be more clear,and the amount of radiation absorbed by the patient will be more small,able to achieve high-quality inspection images with a short-time,low-dose exposure.Therefore,the demand for high-voltage,high-frequency X-ray generators and DC high-voltage power supplies with higher stability and higher reliability are significant.The dissertation mainly studies the high voltage inverter power supply and the filament power supply in the DC high voltage power supply of X-ray machine.Summing up the common topological structure of high-voltage inverter power supply,because LCC resonant structure can absorb parasitic parameters in step-up transformer,therefore,LCC resonant converter is used as the main inverter topology of high-voltage inverter power supply,and the working characteristics of LCC in CCM mode are developed.In addition,for the current widely used square wave driving filament heating method,there is a problem that the filament current sampling is inaccurate and the current control accuracy is poor.In this paper,a sine wave driven filament heating method based on a class D amplifier is proposed to make the filament operating voltage and current are both Standard sine wave.The paper first analyzes and designs the high-voltage inverter power supply system,including voltage and current double closed-loop control,parallel use analysis of MOS transistors,voltage-controlled oscillator(VCO),high-frequency drive transformer,and design of LCC resonant parameters.The designed resonance parameters are verified by simulation.The simulation results show that the design parameters meet the actual requirements;then the sine wave drive filament power supply is analyzed and designed,mainly including Class D power amplifier,RMS conversion principle and PI controller.Etc.Finally,a high-voltage inverter power supply experimental prototype and a sine wave driven filament heating experimental platform were respectively produced.The experimental results show that the maximum output power of the high-voltage inverter power supply is 65 kW,and the maximum operating frequency is 200 kHz,and the MOSFET in all load ranges can realize ZVS,reach the design requirement;In addition,the error of current control of sine wave drive filament heating is 2.68% at maximum,still less than 3.31% of square wave drive minimum error,verifying that sine wave drive can effectively improve filament current control accuracy and achieve expected effect.